The sorters of the above type can be further divided into the following two types.
Sorters of one type, which are disclosed for example in U.S. Pat. No. 3,604,321 and U.S. Pat. No. 4,170,349, include transport means providing a path of transport of sheets along the inlets of bins, and a deflector unit serving as distributing means and movable in parallel with the path. The deflector unit includes a deflector partly positioned in the path for deflecting a forwarded sheet toward one of the bins in engagement with the sheet and guiding the sheet into the bin.
Sorters of the other type, such as the one disclosed in U.S. Pat. No. 4,322,069, comprise a movable unit having discharge rollers and movable along the inlets of bins, introducing rollers for receiving sheets from a copying machine and two endless belts reeved around the discharge rollers and the introducing rollers for sandwiching the sheet therebetween. With the sorters of this type, the transport means and the distributing means are in the form of an assembly.
Unlike high-speed sorters of large capacity having a diverting gate at the inlet of each bin, the sorters of the types described are compact and simple in construction but still have various drawbacks to be eliminated.
The sorter of U.S. Pat. No. 3,604,321 does not include means for locking the deflector unit in the position where the deflector unit is halted in a position opposed to one of the bins. The sorter of U.S. Pat. No. 4,170,349 includes only a ratchet and a dog for locking the deflector unit against movement in one direction only.
Accordingly the sorters of U.S. Pat. Nos. 3,604,321 and 4,170,349 involve the likelihood that if the apparatus temporarily stops in the event of a jam, the deflector unit will be displaced from the proper position when the operator removes the jamming sheet. If the sorter is thereafter operated with the deflector unit in the displaced position, an error will occur when the subsequent sorting operation is resumed.
The sorter of U.S. Pat. No. 4,322,069 has idle sleeves for pressing the two endless belts against the introducing rollers and the discharge rollers to hold the belts in tension, so that under a stable condition, the portions of the belts between the introducing rollers and the discharge rollers are held tensioned, while the other portions of the belts are in a free state. With this arrangement, however, the belts become relaxed when subjected to a great force between the pairs of rollers, and the relaxation will not be remedied unless the apparatus is disassembled and the belts reinstalled.
Such a great force is produced by the resistance of the sheet, for example, when the discharge rollers are the largest distance away from the introducing rollers. When the pairs of rollers are so positioned, the direction of advance of the sheet while it is being transported while held between the two belts greatly differs from the direction of advance of the sheet when it is delivered from the discharge rollers. The stiffness of the sheet produces resistance to the deflection of the sheet to the latter direction. Such resistance exerts a force on the belt to cause relaxation or permits the sheet to slip in front of the discharge rollers, possibly resulting in a jam or like failure.
Further because the portions of the belts other than those positioned between the pairs of rollers are free, the free belt portions must be accommodated in a considerably large space so as not to interfere with other members. It is therefore impossible to make the arrangement very compact.